First Time - Dib X Mabel
by Invader Sam
Summary: 10 years after their first meeting, a reunion of the Mystery Kids leads Dib and Mabel to realize, and act on, their feelings for each other. One-Shot Lemon. Part of my crossover headcannon, further explored on my Deviant art page: :/ invader-sam . deviantart . com / gallery /


"You shouldn't let him get away with that, you know."

"Hmm?" Mabel looked up from the Instagram feed on her phone to the lanky paranormal investigator seated next to her on the den couch. "Let who get away with what?" she asked.

Dib's long fingers gripped the plaid couch cushions tightly. "You know who I mean," he said, cheeks flushed beneath his glasses.

"Huh? You mean Zim?" she guessed, watching him closely. "What do you think he got away with?" She had a good hunch, but she wanted to hear him say it. It was fun watching the young man fidget uncomfortably in his seat as he worked to articulate himself.

"He…well he, er, he _used_ you," Dib finally managed. "Earlier."

She couldn't help but laugh. The alien, who had remained child-sized while the rest of them had grown, had spent much of the afternoon in her lap, contentedly letting her coddle him. "Oh c'mon. You know he was just doing that to get Dipper all bent out of shape," she said. "And you too, I see. But I gotta tell ya, you're objections on behalf of my honor would hold a lot more weight if you weren't actually super jealous." She gave him a light punch to the upper arm.

"W-what?!" he stammered, rubbing his arm as if she'd actually hurt him. "That's not, I mean, I wasn't –"

"Please," she said, reaching out to take hold of his wrist. "Here." She placed his hand squarely on her right breast. "You feel better?"

The color drained from the already pale young man's face and his jaw went slack. Even through her sweater, he could tell she wasn't using any padding. The large, soft mound under his fingers was all _her_. _'Is she a 'D'? I was thinking 'C' before but now I dunno…Oh God, is my hand still on it? Am I drooling?! Shut your mouth, moron!'_ He pulled his hand away quickly, and cleared his suddenly very dry throat. "W-why'd you do that?"

"Thought you wanted me to," she said matter-of-factly. "I mean, you like me, right? I kinda got that feeling…" She reached back and pulled the ribbon out of her hair, shaking out the loose ponytail.

"I…I…um," Dib struggled to make his tongue work. "I, uh, I…yeah." _'Yeah? YEAH? That's the best you can do? How about 'I've never stopped thinking about you' or 'I was the first person to subscribe to your YouTube channel'? 'Yeah'? Really?'_ But for all his inner berating , he was rewarded with her smile and his stomach started doing flips inside him.

Mabel reached out again, this time laying her hand over his. "I was hoping you'd say that," she told him, dark brown eyes shining.

He couldn't help but grin. "Really? I mean, wow, I never would've – I mean you're so… _wow_." And then before he could further mentally chastise himself for his lack of eloquence, she leaned in and pressed her lips to his. She tasted like bubblegum. He'd known she would. She'd just recently been singing the praises of her lipbalm online to over 50K subscribers. He never could've imagined he'd like the taste so much.

He felt her hand slip under his t-shirt and pulled back in surprise, cheeks flushed. "W-wait, what're we doing?" he asked.

She cocked her head, still smiling at him. "Well, we've only got this weekend. I figured, ya know, we shouldn't waste time." Her hand was still under his shirt, resting just above his hip.

He could feel the heat rising up his neck and…elsewhere. Was she really suggesting…? "B-but we can't just–"

"Why not?" she asked. She scooted back and pulled her sweater up and over her head.

His list of very-good-reasons-why-this-was-a-bad-idea dissolved as he stared at her. She was stunning – curvy like something out of a Renaissance painting, if Renaissance models wore pink lacey bras, that is. He swallowed thickly. "Th-there's… _everyone_ out there," he said weakly, raising a shaking hand to point at the door.

She rose, padding over to the door and kicking off her ballet flats as she walked. "Grunkle Stan and Grandpa went to the lodge. Soos went home. And the others are watching a zombie movie marathon." She locked the door. "Trust me, they won't hear us."

"But, but we just, I mean it's really, um, _sudden_ ," Dib said, unable to tear his eyes from the young woman as she made her way back to him.

"Relax," she said, standing in from of him, one hand on her wide hip. "It's not like it's anything we haven't done before with other people, right?"

"Er…" _'Speak for yourself.'_ He ducked his head between his shoulders, feeling his ears burn.

"Wait," she said, eyeing him closely as he turned his gaze away from hers. "Oh! Oh, you've never?"

He cringed. _'Dammit.'_ "Not…exactly," he managed, eyes on his shoes. It wasn't for lack of trying, per se, but it was just so easy to get caught up in his work, everything else generally fell to the wayside.

"Oh, hey, that's okay," she said softly. Her hand was on his cheek then, steering his gaze back to her. "I'm sorry. We don't have to if you…I know a first time, you kind of want it to be special."

His heart lurched in his chest. _'Idiot! You've only been imagining this for the last five years! Just go for it!'_ Fighting to keep his hand steady, he raised it and took hold of hers. "S-sorry, I didn't mean to imply…I mean," he swallowed again. "W-with _you_ , it _would_ be."

The smile she gave him next made his heart melt all over again. "Really?"

He nodded. "Really."

"Oh, you're just the sweetest thing!" she said, pulling him close. In their current configuration, this meant his face was pressed up against her considerable bosom.

He felt dizzy. _'God bless that stupid fucking alien,'_ he thought vaguely. He breathed her in, daring to raise his hands up and place them on either side of her waist. "You're, uh, you're sure about this?" he asked, keeping his gaze down. "I mean, I generally know what I'm supposed to do, but I, uh…" he trailed off, unable to finish his thought aloud.

She pulled back slightly, cupping his face in her warm hands. "Just follow my lead. You'll be fine," she said. "Now. Take off my skirt."

"Uhwah?"

"You heard me," she said, smiling. "Zipper's on the side."

He could feel it, and he took hold of the little metal tab in fingers that wouldn't stop trembling, no matter how hard he willed it. Despite that, he managed to pull the tab down until it wouldn't go any further. Then it was just a matter of sliding the material down her thighs, which required just a bit a shimmying. This let him brush his fingers against her skin and he felt his mouth go dry again as her panties (pink, matching her bra) revealed themselves to him. He had to pull back then, his face was too close to such sacred territory and his head was spinning.

If Mabel could sense how overwhelmed he felt, she didn't show it. Instead, she stepped deftly out of her skirt, and then took hold of his arm, pulling him to his feet. "Well, I'm feeling a little underdressed now. Why don't you fix that?"

He stood stock still a moment. He knew what she wanted but his arms weren't cooperating. She was so close, and so gorgeous, her hair lying angelically over her shoulders, he couldn't stop staring.

"C'mon now," she said teasingly. "Don't leave me out in the cold here." She took the lapels of his jacket in her hands and pushed them down over his shoulders.

It was enough to get him focused again, and he tossed the trench coat over the back of the couch. Then he pulled his T-shirt over his head, though he held it in front of himself once it was off.

"Hey now, none of that," she said, taking the garment from him and dropping it to the floor. "Boy, you really don't get much sun, do ya?"

He blushed, rubbing one arm in a subconscious move to cover himself. "N-no, not much."

"I like it," she told him, pushing his arm back down. She ran a finger along his breastbone. "Makes me feel like I'm getting to see something secret, ya know?" A small smile tugged at his lips. "But I don't think you're quite finished, mister."

His smile faltered. He was suddenly thankful he still had his boots on, as it let him delay the inevitable for a moment longer. As he set them aside, he tried to remember what underwear he'd chosen to wear that day. If he'd known something like this would happen (but how could he have?), he would've chosen very carefully. He was slightly relieved to find a dark gray pair of boxer briefs as he unbuttoned his jeans. Totally acceptable. And they also, to a degree, helped hide his growing excitement, even if they made things a bit uncomfortable. He took a deep breath and slid his jeans off, stumbling slightly as he tried to get them fully off.

Mabel caught hold of his shoulders, steadying him. "That's better," she murmured next to his ear. He was thankful she was holding him up, as his knees went weak.

Suddenly she was kissing him again and he let her guide him back to the couch, doing his best to kiss back. The fact that she was only the second girl he'd ever kissed lingered at the back of his mind. He prayed he wouldn't do anything stupid. Eyes closed, drinking her in, he let his hands rest on her sides, reveling in her soft warmth. His fingers brushed the lace of her bra and he was struck by a brave notion. Did he dare? He did. Slowly, his fingers found the clasp and he pinched either end between forefinger and thumb. With blessedly little struggle, it came undone.

"Ooh, nice job," she said, pulling away slightly. "Sure you've never done this before?"

"No, ne–" his words caught in his throat as she slipped out of the supportive garment, her breasts spilling forth before his eyes. "Never," he managed in a whisper. _'Definitely a 'D'.'_ "…Holy…"

She laughed. "Go ahead," she said, leaning towards him. "You know you wanna."

His hands were trembling again, but he forced himself to cup her gently, marveling at the feel. He was suddenly thankful for his long fingers, as he could almost encompass them fully. She had a beauty mark under her right nipple. He felt privileged to now know this.

"Breathe, Dib. Breathe," she said.

He hadn't realized he'd been holding his breath, and took in a gasping gulp of air. "S-sorry," he said. "They're just so… _you're_ _ **amazing**_."

"And you're so sweet," she said, running a hand through his hair. "And not so bad yourself, if I do say so." Her hand slid down his face and then joined its twin to rove over his chest. She grazed his nipples with her thumbs and he sucked in a breath. "You're really cute."

He let out a short laugh. Did she really think so? Would he be in this amazing position if it were otherwise? "Th-that feels nice," he said, feeling his member strain against the constrictive fabric which encased it.

"Yeah it does," she said. "Why don't you try it?"

"Huh?" She pressed her chest further into his hands and he got the hint. "O-oh. Right." He let his thumbs slide over her nipples and rubbed gently. He was instantly rewarded by the sight of her cheeks flushing – the first time that evening. He was surprised at the wave of relief that washed over him. So far it had felt a bit like she was just doing him a favor. Seeing the color rise from her chest to her face gave him hope that he wasn't the only one enjoying the experience. Tentatively, he leaned forward, letting his lips fall on her collar bone. She let out a soft, affirmative murmur, which encouraged him. Releasing her breasts (hard as that was to do), he instead rested his hands on her sides, running kissing up her neck.

She let out a low giggle and began running her hands through his hair again. His lips found a hollow spot right where her neck met her torso and she gasped. Confidence bolstered, he focused on that spot, kissing and nipping it gently. When he tried to suck at it, however, she pulled him away with a light tug at his scythe. "Easy now," she said. "I'd rather not have to explain a hickey to Dipper or the old guys."

"Oh, heh, right, sorry," he said sheepishly.

"You on the other hand, I'm not so worried about."

"Huh?" But rather than answer, she descended on his throat, kissing all along it. He didn't have the will to protest. It felt too wonderful and he let his shoulders slump, giving her easy access for her affection. Then she was sucking at the spot he'd just tried to and his stomach gave another flip. A shuddering moan sounded in his ears and it took him a moment to realize the sound had passed from his own lips.

She raised her head after a long moment. "Ya like that, huh?"

He nodded. "That was…that was really nice."

"I love how enthusiastic you are," she said, twirling his scythe around an index finger. "And we haven't even gotten to the really good stuff yet."

"I-it's _all_ really good stuff," he assured her.

She grinned, and then stood. "Glad to hear it." In one swift motion, she slipped off her panties and kicked them aside, leaving him dumbstruck again. With a giggle, she leaned forward and tapped his chin, causing his mouth to snap shut. "A girl could really get used to this kind of reverence, ya know."

He blinked a few times, willing his eyes up to her face. "Y-you deserve it," he said breathily.

"You really are sweet," she said, and kissed him, one hand on his shoulder. "Now, how about we even the score, hmm?"

"Hm? Oh, uh, right. H-hold on." He took another deep breath. _'Ok, here goes. What's the worst that can happen?'_ He tried not to think about that, instead focused on removing his boxer briefs with as much grace as possible while still seated on the couch. To his dismay, the constricting nature of the tight fabric resulted in his member practically springing to attention the moment it was freed. He winced, feeling his whole face burn.

But rather than laugh, as he'd expected, Mabel knelt down in front of him, slid the garment down over his knees and helped him step out of them. "There we go," she said softly, running her hands up and down his thighs.

He let out a panting gasp. Her hands drew closer with each pass up his legs and his erection twitched each time they almost touched it. At last she laid one hand on it and he couldn't stop the squeaking cry from escaping his lips. He'd touched himself plenty of times – what red-blooded American boy hadn't? – but it had never felt like this. Her hand was so soft, so warm. _'Oh God…Oh no. No, no, no not yet – do something!'_

With a little more franticness than he'd intended, he reached out and grabbed her by the wrist. She looked up at him, head tilted. "Hmm? What's up?"

 _'Think of something – Say something – ANYTHING!'_ "I-I w-wanna touch you," he stammered. _'Well that was certainly something.'_

"Boy, can I pick 'em or what?" she said, smiling widely. She released her hold on him and stood. "Okay, well, how do you want me?"

 _'Shit.'_ "Um," he took a quick survey of the room. "Er, I think the couch is deep enough to fit us both. M-maybe we could, uh, lie down together?"

"Yeah, sure!" she nodded. As they arranged themselves on the sofa, he was thankful for the distraction. He felt much less on the verge of finishing too soon. Plus, he now had Mabel's head cradled in the crook of his arm and the whole length of her pressed against him, which was incredible.

 _'Just one problem – what now?'_ He cleared his throat. "Y-you comfortable?" he asked.

"Mmhmm," she nodded. "For are skinny as you are, you're not as pointy as I thought you'd be."

He chuckled at that. "Well, I guess that's good." _'Okay, you can do this. Just be cool.'_ He began running his free hand over her stomach and then, because they were right there, up and over her breasts again. She let out a little sigh. He felt himself relax just a little. He could almost approach this scientifically. Not clinically, but like an exploration. This was his first time with unfettered access to a naked girl after all. "You really are beautiful," he said quietly, his fingers tracing her collar bone, then her rounded jaw line.

She blushed. "And you really are a charmer."

He ran his hand along her side. "Just honest." At her hip he hesitated, then decided that her thighs needed exploring first. No need to rush right in, especially when he was a little fuzzy on what he would be rushing in _to_. This proved a good idea in more ways than one. Firstly, her thighs were a joy to touch, smooth under his fingers and warm. He was consistently struck by her warmth. Perhaps it was just human contact that was the foreign marvel – he had so little of it generally. His family was less than affectionate, to put it mildly.

And secondly, Mabel seemed to be really enjoying this type of touch. She had closed her eyes and was biting her bottom lip a little. She shifted a bit on the couch and he watched in awe as she spread her legs as his fingers glided up the inside of her thigh. _'Oh God…ok, here goes…'_ His hand hovered over her mound, which she must have had waxed, and slowly, cautiously, let it graze her skin.

She let out a tiny gasp and his eyes shot back to her face. Her lips were parted and on impulse, he kissed her. To his surprise, he felt her tongue enter his mouth. _'She must like this, right?'_ When they separated, she was smiling up at him. "You're doing fine," she murmured.

"Just, um, just tell me w-what you like, okay?" he said.

"Well, you hovering your hand like that is driving me _crazy_ ," she admitted, resting a hand on his chest.

"Yeah?" he asked, raising an eyebrow.

"Yeah, crazy as in, I'm gonna jump you soon if you keep teasing me," she said with a smirk.

"O-oh! Okay, right," he said, slightly flustered. The mental image of her jumping him was a hard one to shake. So, with a concerted effort, he lowered his hand again, slowly exploring her folds with his fingers. She clutched at his side suddenly, which he took to be a good sign. Also a good sign: the surprising amount of heat radiating from this particular area of her body. If he'd been struck by her general warmth, this was mind blowing. His middle finger found a small nub between the two larger mounds and when she let out a bitten off cry, he knew he must've found the right spot. He tried stroking it, which she seemed to like, but then he tried rubbing it in tiny circles and she actually gasped his name. Trying to ignore how incredibly hard that had made him, he kept rubbing.

She was panting now, and raising her hips slightly off the couch. His finger slipped as he wasn't prepared for her movement and dipped lower, between the folds and he felt wetness. His member twitched instinctively. "Holy…"

"Oh God, Dib," she said, and he felt her short nails digging into his side. "Please put it in."

He felt dizzy all over again. "Uh, y-you mean my finger…or…?"

"Either one," she said, opening her eyes to meet his terrified gaze. "I'm ready for you."

 _'But am I ready for this?'_ With their eyes locked, he nodded, and pushed himself up so he could position himself over her. He was surprised to find his member was dripping something clear and slick.

"Perfect," she said breathily. She took him in one hand and stroked a few times, making him gasp. Then, she was spreading the clear liquid all up and down the length of him. "That'll help," she told him. "Now go slow to start, okay?"

His ears were ringing, but he nodded and watched in awe as she guided him to her entrance. It took a few tries, but she never let on that that wasn't normal and he couldn't have been embarrassed even if he'd wanted to be. The feel of his tip continually pressing against her wet opening was all-consuming.

And then he was in and it was everything he'd imagined and a thousand times more and he just stayed still for a long moment, swallowing and blinking. "Oh geezus, Mabel," he said shakily. "C-can I move?"

"Mmhmm," she nodded, taking hold of his hips with both hands. "Just start slow."

"Slow, right, okay." He eased nearly all the way out and then slid back in. She raised her hips slightly to meet him. He could feel her press against his pubic bone and he shuddered. Another out and in and then another, with her hands setting the rhythm. It felt so good it almost hurt.

His eyes shut automatically and he forced them open. He wanted to see this – to see her. Below him, she was smiling up at him, her hair pooled around her, a few errant strands clinging to her forehead. He was glad he wasn't the only one sweating. "This…feels…so good," he panted.

"Damn straight," she said, lifting her head up to kiss him. He felt her hands leave his hips to cup his face and then her legs were wrapping around him, her ankles crossed right at his backside. _'Oh Good God…'_ Unable to stop himself, he started to speed up. She pulled away from the kiss and he watched as she slid a hand between them. _'Holy…she's touching herself. That's so hot.'_ He tried to concentrate, tried to keep his pace steady, but it was impossible. His body seemed to be moving without his input, taking him for this intoxicating ride he wished would never end. But alas…

"M-Mabel," he gasped. "I can't…I'm gonna…"

"Go ahead," she half-whispered. "Just stay put when you do. I'm almost there with you."

That statement alone was enough to nearly send him over the edge. Another few thrusts and he came fast and hard into her, stars dancing in front of his eyes, moaning loudly. His whole body shaking, he was able to focus just enough to watch her come a moment later, her inner walls tightening around him and making him cry out again. Her climax seemed to last longer than his had, if her continued mewling cries were any indication, and he tried to stay still for her as she'd asked, but his hips jerked involuntarily. Thankfully this only seemed to bring her more pleasure, so while the sensation was so intense he could barely stand it, he kept it up until she put a hand on his chest. "Okay, okay, I'm good," she panted. "Hoo boy am I good."

He choked back a laugh at that, and they, unable to stop himself, erupted in a half-stifled fit of giggles. She joined him in his mirth, wrapping her arms around him tightly, pressing her cheek to his. "I take it that you're good too, then?" she asked.

He nodded. "More than good." _'I love you.'_ He froze, petrified he'd spoken the words aloud. But her demeanor didn't change. He was safe. True as the statement might be, it wouldn't be right to spring it on her in this moment. Instead, he said, "Can I thank you?"

She laughed harder at that. "I guess so. But I didn't initiate this to do you a solid. I really like you, Dib."

 _'Oh thank God.'_ "I really like you too."

"Then you're welcome," she said with a smirk. "Now…do you think you can reach the box of tissues on the end table?"

"Probably. Why?"

"Well, because we're kinda gonna make a mess when we separate and I want to get as little of it on the couch as possible."

"Oh, right, sure." His long arms proved more than sufficient to retrieve what she asked. Then, as he handed it to her, a horrifying thought struck him. "Oh my God. We…we didn't use any protection!" _'Idiot! That's what you get for not coming prepared! As if you could ever have expected this!'_

"Hey, hey, easy," she said, patting his cheek. "I've been on the pill since my last boyfriend, back in junior year. We're good. I promise. I wouldn't have done this otherwise."

He let out a sigh of relief, letting his forehead fall against her chest. "Okay. Good. Sorry."

She patted his head. "No worries. Hey…are you still wearing your glasses?"

"Huh?" He lifted his head, then brought a hand up to his face. "Yeah, guess I am."

She smirked. "You dork."

"H-hey!" he protested. "I'm pretty blind without them and I…I wanted to _see_ you," he admitted, a fresh blush creeping across his face.

At that, she kissed him again. "Aw, I really _can_ pick 'em! Alright, I need you to grab a handful of tissues and back up slowly, okay?"

"Right, you got it." It was a careful operation but they managed to separate with minimal mess, though the waste basket was conspicuously full of tissues when they were done. As he gingerly stepped back into his boxer briefs (things were still sensitive down there) he said, "Really, though, thank you. I never thought, when I agreed to come up here for the weekend…I mean, just, **_wow_**."

Mabel snapped her bra back in place and then sidled up to hug him from behind. "I meant it before. I really like you. I'm hoping that maybe, when you go back home, you might call me sometime."

He smiled. "How's video-chat sound?"

"Even better."

"And you know, I'll have to find my way to California eventually," he said, putting a hand over hers, which we clasped about his middle. "Because this was too amazing to be a one-and-done thing."

"Agreed," she said. She pressed her lips to his neck. "We've got lots of good grad schools out there."

"Then I'll just have to start sending out applications." He turned so he could face her. "And until then, well, we've still got the rest of the weekend."

"That's right! What would you like to do? Go watch zombie movies with the others, or sneak out the back and go get post-sex pancakes at the all-night diner?"

He leaned in to kiss her. "Pancakes. Totally pancakes."

"All right! We better get dressed then!"

"Yes ma'am," he said with a laugh.

Together they hurriedly dressed and he followed her out into the moonlit summer night, smiling like he'd never smiled before.

-Fin-

* * *

 **Author's Note: This is part of a larger crossover headcanon, which has been further explored on my Deviant Art page: gallery/ Please go check it out! ^_^  
**


End file.
